More than any other species of trilobite, Dalmanites is the one most often see for sale from the Rochester Shale. I purchased this nice little pyritized specimen of Dalamnites limulurus from a rock shop in Basdell, NY (Past and Present). It's smaller than most that I see offered but I like the golden pyrite look and the slight twisting of the fossil.
This is most likely a molt but the way that the body is slightly twisted and bent makes it look like it died in place. Maybe smothered by anoxic conditions (which would explain the pyrite preservation)?
The specimen came from the Rochester Shale which is dated to the
Sheinwoodian/Homerian stage of the Wenlock epoch of the Silurian.
I had a much larger specimen that I blogged about here.